Processes of making lithographic reproductions



- UNITED. STATES PATENT OFFICE PROCESSES OF MAKING LITHOGRAPHICREPRODUCTIONS Fred Harvey Bloom, Fort Belvoir, Va.

No Drawing. Application June 18, 1936, Serial No. 85,929

14 Claims.

(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) This invention described herein may be manufactured and usedby or for the Government for governmental purposes, without the paymentto me of any royalty there This invention is a continuation in part ofmy pending application, entitled Processes of making lithographicreproductions, filed December 20, 1934, Serial No. 758,456, and relatesto the art of lithography; more especially it is directed to a processfor the production of a lithographic plate having a light sensitivesurface selectively responsive to the tone values of a negative, thelight affected areas of the plate being sufiiciently hardenedv afterexposure to permit the immediate transfer of the plate to the press forprinting purposes without further manipulation other than the usualwashing treatment with developing ink and drying.

One object of this invention is to provide a process for the productionof lithographic plates by means of which a photographic negative ingraduated tones, or a photographic line negative or their combination,may be transferred directly to a lithographic plate without the use ofsuch intermediaries as cameras, the like.

half-tone screens and Another object of this invention is to provide aprocess for the production of a lithographic plate surfaced with a lightsensitive substance intimately combined with a light absorbingdesensitizing material, the mixture functioning to form a lightsensitive film adapted to be hardened selectively in accordance with thetone graduations of the negative.

Another object of this invention is to provide a process for theproduction of lithographic plates wherein an ammonium bichromatesolution is intimately combined with an albuminous dye substance, themixture when of a metallic plate and drie applied to the surface d,providing a printing plate which may be used for printing directly fromthe negative, so that, the proceeding from the exposure to the finishedplate, may be accomplished in a few minutes and with better 0 resultsthan are now possible by the use of lithographic methods requiring amuch longer time interval.

Other objects of this inv ention are; to produce a lithographic plateaffording an image which occasion demands; to provide a lithographicprocwhich clear, evenly colored reproductions ess by are obtained overan exten ded period and at high press speed; and to provide a process bywhich a lithographic plate may be produced with less labor and expenseand in a shorter time than has heretofore been possible in this art.

Photo-mechanical reproductions are usually made as follows:

Line drawings A negative is placed in a printing frame in contact withthe coated surface of a sensitized plate and exposed to the rays of anarc lamp for a suitable time interval depending upon the subject Tonegraduation work A positive photographic print of the subject is securedand rephotographed using a half-tone screen to produce a half-tonenegative in which the subject has been broken up into dots, the numberand size of which depend on the mesh 25 of the screen. After thishalf-tone negative has been developed and dried, it is ready to beexposed to the light in contact with the sensitized plate. From thispoint on, the procedure is similar to that described in connection withline drawings, except it involves more etching, counter-etching androlling up. Moreover, the production of a half-tone printing plate inaccordance with the preceding mode of operation, quite frequentlynecessitates several half-tone negatives before a satisfactory plate isobtained, as the dots are sometimes so small, they readily wash ofi,even though hardened by exposure to light.

The preceding lithographic methods, embody limitations with respect tomanipulation and expense, which workers in this field have attempted toovercome through the use of processes which enable the plate to beprinted directly from the negative without the use of intermediaries inthe nature of cameras and screens. Most of these effortshave includedthe use of a lithographic plate having a light sensitive surfacecomposed of a chromatized colloid. These methods however, have to alarge extent been cast aside, as the images produced lacked the strengthand flexibility necessary to withstand long press runs at high speed.This want of flexibility and strength as the run progressed resulted inunevenly colored and blurred prints.

It is therefore the aim and purpose of the instant invention to producealithographic plate, which after exposure for the prescribed timeinterval and when washed, inked and dried may be transferred to thepress and utilized to produce clear, even-colored reproductions. Thisresult has been obtained by the use of-an albuminousdye-mixtureintimately combined with an ammonium bichromate solution, the mixturebeing automatic in its operation, so that when any portion of thenegative has been exposed to light for the time interval required toproperly print that portion of the negative, the light affected areas ofthe plate are so hardened as to retard subsequent action of the lightrays and hence such portions will not be further materially affected bylight rays within the exposure period. Each graduation of tone as itreceives the required exposure is similarly hardened by the light actionand the result is that no portion of the plate will be over-exposed,assuming a reasonable exposure limit.

Thus a lithographic plate is provided by means of which it is possibleto print a photograph direct from the negative, securing the proper tonevalues for all parts of the negative, and the full amount of detailcontained in the negative. short, the instant invention provides in alithog aphic plate production, all that the same negatii/ would give inan ordinary photographic print on paper, with exception of loss-indetail caused by the plate. This loss of detail, never large, variesinversely with the fineness of the grain of the plate.

To carry the present invention into effect the procedure is as follows:

Preparation of the sensitizing solution tion. This mixture is stirredwith a stirring rod until the albumen has absorbed suificient water toappear moist and when this has occurred it is gently agitated with anegg-beater'until all of the albumen has been dissolved, and then allowedto stand from three to five hours, the time required to reduce the heavyfoam produced by the eggbeater, to a thin layer.

Ammonium bichromate solution To provide a suitable ammonium bichromatesolution for this process, 322 grains of ammonium bichromate aredissolved in four ounces of hot water. The solution is then slowlyfiltered into a thirty-two ounce graduate through absorbent cotton. Thisfiltering operation should be carried out with a clean glass funnel intothe bowl of which there has been placed a piece of suitably moistenedabsorbent cotton about three inches square. The center of the piece ofabsorbent cotton should be forced'into the neck of the funnel with astirring rod or'the like, but care should be exercised not to pack thecotton to an extent which would interfere with the filtering process.

Immediately after the ammonium bichromate solution has been filtered,the pheno-safranineegg-albumen-mixture is poured into the bowl of thefunnel, the thin layer on the surface of the albumen mixture having beenfirst removed.

' acid to one gallon of Before the contents of the funnel have startedto filter through, a half of monia (25 Baum) is added. The solution isthen slowly filtered into the graduate containing the ammoniumbichromate filtrate. When the filtration oi theegg-albumen-pheno-sai'ranine-ammonium solution has been completed thecontents of the graduate, which should be about twenty-four ounces, arerefiltered and the resulting filtrate poured into acontainer preferablya colored bottle.

Although in the preceding description phenosafranine identified in thecolor index of the Soclety of Dyers and Colorists, published January1926, as diamino-phenyl-diphenazonium-chloride, color index No. 840, hasbeen designated as the desensltizing dye, it is to be understood thatvarious other desensltizing dyes such as-Pinocryptol Green, MethyleneBlue, Rhodamine, Malachite Green, and ictoria Blue may be employed.

In the color index of the Society of Dyers and Colorists, publishedJanuary, 1934, the preceding dyes in the order of their enumeration havethe following color index numbers: 824a, 922, 761, 657-3, and 729respectively.

Coating the plate Before receiving its sensitizing coating, the plate isplaced under a water tap, swilled and treated with a solution consistingof two ounces of nitric acid and four ounces of potassium alum to onegallon of water. Instead of the nitric acid and potassium alum solution,just mentioned, a solution consisting of two ounces of glacial aceticwater may be used. After the plate has been treated with one of thesesolutions (a piece of cheese-cloth being preferably used for thispurpose), and while it is still wet, the plate is fiowed hereinabovedefined. The sensitizer is usually distributed over the face of theplate and'dried by means of a whirler, rotating at 'a speed of aboutsixty revolutions a minute. When it has been dried the plate should beplaced in the vacuum printing frame without undue delay.

Exposure of the plate The plate having been suitably mounted in thevacuum printing frame, it is exposed under a negative to a thirty ampereopen are light at a distance of approximately 30 inches. The time ofexposure for the average negative is one minute and forty-five seconds.Denser negatives require a longer, thinner or flat negatives lessexposure. Should the negative be very dense it is advisable to shortenthe distance of the are light from 30 inches to 26 inches, and in theevent the negative is very flat or thin, the distance of the are lightfrom the printing frame should be increased to 34 inches. All of theabove distances and exposures are based on a 30-ampere open are light.

The plate having been removed from the vacuum printing frame is treatedwith an even coating of developing ink applied with a piece of cotton.The plate is then dried for a short period.

Clearing the plate After receiving its coating of developing ink theplate is placed in a tray of water, the latter being at a .temperatureof 90-97 F., and in a few seconds the image appears, whereupon thebackground is removed, using for this purpose a moist piece of cotton.Care should be exercised in the ounce of strong amwith the sensitizingsolution hasty treatment during this operation, 111812;?"

suit in a ruined plate. A rotary motion with the cotton is recommended,as rubbing from right to left and up and down may produce a streakyimage. Should difficulties be encountered in the operation of clearingthe image due to overexposure, it has been found expedient to aidremoval with a solution consisting of four tablespoons of sodiumbicarbonate to one gallon of water. This solution is applied by dippinga wet piece of cotton into the bicarbonate solution and applying it tothe entire plate surface. After the plate has been treated with thebicarbonate solution, the removal operation is continued as prev'ouslystated. When satisfactorily cleared, the late is dried and thenpositioned on the press for the run. In the event the plate is not to beused immediately, it is gummed and filed.

The procedure for reproducing line drawings from plates prepared inaccordance with this invention, with exception of the exposure interval,is similar to that described in connection with the reproduction ofphotographs, portraits and the like. The exposure interval for linedrawings may cover a period of from one to fifteen minutes, withoutruining the plate. This flexibility of exposure constitutes quite an aidto a novice in the art, owing to the assurance which it gives.Alteration of the image on a plate produced as hereinabove described,becomes a comparatively simple matter. For instance, should it benecessary to make an addition to the image on the plate, the latter isswilled and treated with a weak hydrochloric acid solution consisting ofone ounce of hydrochloric acid and one gallon of water. After thistreatment with the hydrochloric acid solution, the requisite addition ismade using for the purpose, a preparation commercially identified asTusche. When the addition has been made the plate is allowed to standapproximately thirty minutes, until the work has been dried andhardened. To remove a portion of the image on a plate the latter isswilled and the undesirable part of the image erased by means of asnake-stone or gamberger stick. After the erasure, the plate is againswilled and treated with the hydrochloric acid solution as in making theaddition.

In conclusion, it is evident the instant invention materially simplifiesprocedure in the lithographic art and makes it possible for anindividual possessing but little experience in this field, to be trainedso as to be able to produce excellent lithographic reproductions in arelatively short time.

Having described my invention, what I claim as 'new and wish to secureby Letters Patent is:

1. A process for producing a printing plate, consisting in treatingegg-albumin in the presence of heat with a light desensitizing-dye, thenafter allowing the albumin and dye mixture to stand for a predeterminedperiod, combining the mixture with an ammonium bichromate solution, thencoating a plate with this chromatized mixture to form a light sensitivesurface adapted to be selectively hardened in accordance with the tonevalues of a negative, exposing the surface to the action of light, thelight affected areas of the surface, when hardened by exposure, beingfurther unaffected to any material extent by light rays during theexposure period and then inking, washing, clearing and drying.

2. A process consisting in introducing egg albumin into a lightdesensitizing-dye solution in the. presence of heat, then after allowingthis solution to stand for a period of three to five hours, combiningthe dye-treated albumin with an ammonium bichromate solution, thencoating a plate with the mixture thus formed, to produce a lightsensitive surface adapted to be selectively hardened in accordance withthe tone values of the negative, then exposing said surface to theaction of light, the light affected areas of the surface hardened byexposure, being further unaffected to any material extent by the lightrays during the exposure period and then inking, washing, clearing anddrying.

3. A process for producing a printing plate consisting in introducingegg albumin into a light desensitizing dye solution in the presence ofheat and within the temperature range of 120 to 135 F., allowing thissolution to stand from three to five hours, combining the mixture withan ammonium bichromate, solution, then coating a plate with the chromatid mixture to form a light sensitive surface adapted to be selectivelyhardened in accordance with the tone values of the negative, exposingsaid surface to the action of light, the light affected areas of thesurface when hardened by exposure, being further unaffected to anymaterial extent by the light rays during the exposure period and theninking, washing, clearing and drying.

4. A process for producing a printing plate which consists in preparinga light desensitizing dye solution adding eitherpowdered or flaked eggalbumin to the dye solution in the presence of heat, then after allowingthis mixture to stand from three to five hours, combining the solutionwith an ammonium bichromate solution, coating the plate with thischromatized mixture to form a light sensitive surface adapted to beselectively hardened in accordance with the tone values of the negative,then exposing said surface, the light affected areas of the surface whenhardened by exposure being further unaffected to any material extent bylight rays during the exposure period inking, washing, clearing anddrying.

5. A process for producing a printing plate consisting in preparing alight desensitizing dye solution, adding either powdered or flaked eggalbumin to the dye solution in the presence of heat, then after allowingthe mixture to' stand from three to five hours, combining it with theaddition of ammonia, to an ammonium bichromate solution to form a lightsensitive surface adapted to be selectively hardened in accordance withthe tone values of the negative, exposing said surface to the action oflight, the light aifected areas of the surface when hardened by lightbeing further unaifected to any material extent by light rays during theexposure period inking, washing, clearing and drying.

6. A process for producing a lithographic plate, consisting in preparinga light desensitizing dye solution, introducing egg albumin into thesolution in the presence of heat and within a temperature range of 120to 135 F., then after allowing the mixture to stand from three to fivehours adding ammonia with the addition of an ammonium bichromatesolution, coating a printing plate with the chromatized mixture to forma light sensitive substance, adapted to be selectively hardened inaccordance with the tone values of the negative, exposing said surfaceto light, the light affected areas of the surface when hardened byexposure, being further unaflected to any material extent by light raysduring the exposure period inking, washing, clearing and drying.

u HHH HHHHHHH H 7. A process for producing a printing plate, consistingin preparing a, diamino-phenyldlphenazonium-chioride solution,introducing egg albumin into the solution in the presence of heat andwithin a temperature range of 120 to l35 F., then align allowing themixture to stand from three to five hours, adding the mixture, with theaddition of ammonia, to an ammoniumbichromate solution and then coatinga printing plate with the mixture to form a light sensitive substance,adapted to be selectively hardened in accordance with the tone values ofthe negative, exposing said surface to the action of light, the lightafiejyedareas of the surface when so hardened to e .posure of light,being further unaifected to any material extent by light rays during theexposure period inking, washing, clearing and drying.

8. A light sensitive element comprising a'sub-' stantially gelatin-freeegg-albumin, treated in the presence of heat with a light desensitizingdye and containing a chromatizing agent and which after exposureto'light and without fur- I ther treatment other than inking, washingand clearing, will produce clear and evenly colored prints at high speedand over an extended press run.

9. A light sensitive element comprising a 'substantially gelatin-freeegg-albumin, treated in the presence of heat and within the temperaturerange of 120 to 135 F., with a light desensitizing dye and containing achromatizing agent and which after exposure to light and without furthertreatment, other than inking, washing and clearing, will produce clearand evenly colored prints at high speed and over an extended press run.

10. A light sensitive element comprising substantially gelatin-freeegg-albumin treated in the presence of heat with a light desensitizingdye and containing an ammonium bichromate, and which after exposure tolight and without further treatment other than inking, washing andclearing, will produce clear and evenly colored prints.

11. A light sensitive element comprising substantially gelatin-freeegg-albumin treated in the presence of heat and within a temperaturerange of 120 to 135 5., and with a light desensitizing dye containing anammonium bichromate, which after exposure to light and without furthertreatment other than inking, washing and clearing, will producenon-blurred and evenly colored prints at high speed and over an extendedpress run.

12. A light sensitive element comprising a sub= stantially gelatin freeegg-albumin treated in the presence of heat with pheno-safranine andcontaining a .chromatizing agent and which after exposure to light andwithout further treatment other than inking, washing and clearing, willproduce clear and evenly colored prints at high speed.

13. A light sensitive element comprising a substantially gelatin freeegg-albumin treated in the presence of heat with pinocryptol green, andcontaining a chromatizing agent and which after exposure to light andwithout further treatment other than inking, washing and clearing, willproduce clear and evenly colored prints at high speed.

. 14. A light sensitive element comprising a substantially gelatin freeegg-albumin treated in the presence of heat with methylene blue, andcontaining a chromatizing agent and which after ex- .posure to light andwithout further-treatment other than inking, washing and clearing, willproduce clear and evenly colored prints at high speed.

FRED HARVEY BLOOM.

